1. Field of the invention
The invention relates to an apparatus and method for handling solids carried in a liquid, for example for pumping fish in water from a net or hold of a ship into another receptacle.
2. Prior Art
For many years, fish and other delicate solids such as fruit and vegetables, have been carried in water to facilitate handling and reduce damage thereto. A common problem associated with handling such delicate solids in liquid is that the solids themselves should not pass through the pump or other means moving the liquid. One way of reducing damage to the solids is to draw the solids into a receiving chamber which has been evacuated by a vacuum source, followed by emptying the solids from the chamber by disconnecting the vacuum source, and admitting atmospheric air, or air under pressure, into the chamber to discharge the solids and liquid therefrom. The liquid is usually separated from the solids after discharge, and is returned to the container, or exhausted to waste.
One problem with prior art pumps of this type results from the fact that solids passing through the inlet valve of the chamber are sometimes trapped by the inlet valve when the valve is being closed following admission of additional air into the chamber, usually when the chamber is approaching a full condition. This is particularly prevalent when pumping fish, which are usually elongated and are more prone to interferring with the inlet valve that shorter objects, such as fruit. While small fish effectively can be cut by the inlet valve to permit closure thereof, larger fish restrict the inlet valve against closure, and then it is impossible to evacuate the chamber without first clearing the blocked inlet valve. This requires shutting down the machine, and usually removing an inspection cover to permit manual removal of the trapped fish.
There are many types of fish pumps, some using one chamber, others using two chambers in parallel which are alternately exposed to suction. U.S. Pat. No. 3,871,332 (Hayashi) shows an inlet valve located adjacent a lower portion of the chamber, which location tends to aggravate blocking of the valve with fish due to a hydrostatic head acting on the inlet valve, the head being proportional to depth of the inlet valve below an upper level within the chamber. This patent also discloses a complex electrical control system to control operation of the valves. In other apparatus it is also known to locate the inlet valve adjacent an upper portion of the chamber, thus obviating the problem of the hydrostatic head, but such location is still prone to fish blocking the inlet valve when flow through the inlet valve ceases.